CN115103765A - Recyclable packaging paper with high barrier to water vapor and oxygen - Google Patents

Abstract

A packaging paper laminate that has high barrier properties to water vapor, oxygen and/or aroma, is easy to recycle, and is easy to manufacture, characterized in that the barrier film (3) comprises at least one substrate layer (4), a connecting layer (5) and a barrier layer (6), the connecting layer (5) is arranged between the substrate layer (4) and the barrier layer (6), and the substrate layer (4) is mainly composed of polyethylene or polypropylene , the polyethylene or polypropylene content is at least 60% by weight of the substrate layer (4), at least one substrate layer (4) of the barrier film (3) is at least stretched, and the paper layer (2) ) in a proportion between 50% and 90% by weight of the wrapping paper laminate (1) and the barrier film (3) is connected to the paper layer (2) with a hydrophilic adhesive layer (9), wherein The side of the paper layer (2) facing the barrier film (3) is uncoated.

Description

Recyclable wrapping paper with high barrier to water vapour and oxygen

The present invention relates to a recyclable packaging paper laminate consisting of a paper layer having a basis weight of paper of 30 to 360 g/m ² and a barrier film connected to the paper layer, said material in addition to recyclability In addition, contain high oxygen, water vapour and/or aroma barriers at the same time.

Wrapping paper laminates are used in the packaging industry and should have different properties depending on the application. This wrapping paper laminate is usually laminated with multiple layers of plastic films that are produced in extrusion processes, co-extrusion processes (in both cases in flat and blown film processes) or Lamination process (connection of the individual layers by means of laminating adhesives) and production in hybrid processes. Layers not made of plastic can also be integrated in the wrapping paper laminate, for example layers made of aluminium or other paper. The wrapping paper laminate also typically has an outer sealing layer for heat sealing the wrapping paper laminate into the desired package, such as pouches, large bags, mid-bags, and the like.

Typical requirements for wrapping paper laminates are barrier functions against water vapour, oxygen and aroma. For this purpose, wrapping paper laminates usually comprise a barrier layer made of aluminium or a suitable barrier polymer, such as ethylene-vinyl alcohol copolymer (EVOH) or polyamide (PA).

Likewise, wrapping paper laminates typically also contain a sealing layer to enable the wrapping paper laminate to be processed into a package by heat sealing. The sealing layer is usually made of polyolefin, usually polypropylene (PP) or polyethylene (PE) with various densities of LLDPE, LDPE, MDPE or HDPE (also as a mixture or with multiple layers of the same or different types).

Other layers may also be included to provide the wrapper laminate with desired properties such as toughness, stiffness, tear resistance, and the like.

In order to be able to process the wrapping paper laminate easily, the wrapping paper laminate must of course not be warped or curled during processing (so-called curling), which is why laminated plastic films usually have a symmetrical layer construction.

In addition, it is known to alter the properties of a wrapping paper laminate by uniaxial or biaxial orientation of the plastic layers of the wrapping paper laminate. This orientation can be carried out by an extrusion process, for example in a multiple bubble process, or only after the extrusion process by machine direction (along the machine direction of the wrapper laminate) and/or transverse direction ( The plastic film was stretched (Recken) perpendicular to the machine direction. The orientation of the plastic film can in particular increase rigidity, tensile strength and toughness.

But it should be noted here that in blown film extrusion and flat film extrusion, the extrusion gap (blown film is 1.5 to 2.5 mm) or the gap of the extrusion nozzle is significantly larger than the final thickness of the extruded film (generally between 10 mm and 10 mm). and 200 μm). To do this, the extruded melt is stretched to a final thickness at a temperature well above the melting point of the extruded polymer. For example, in blown film extrusion, the melt is typically stretched by a factor of about 2 to 3 in the transverse direction (the so-called blow-up ratio) and 1:10 to 1:100 in the machine direction (the so-called draw ratio). However, this stretching during extrusion cannot be compared to stretching of plastic films, since stretching is usually performed at temperatures just below the melting point of the polymer (usually 5°C to 20°C lower), causing disorder The polymer and semi-crystalline regions are stretched to align the stretch direction. In so-called MDO stretching (in the machine direction only), a stretching gap (distance between rolls) of 40-100 mm is generally used. In the case of biaxial stretching, transverse stretching is then carried out in a heated oven.

Especially for ecological reasons, paper is often used as packaging material because it is easy to recycle. However, due to the usual requirements for packaging materials, such as barrier function against water vapour, oxygen and/or aroma, or tightness for packaging production, paper alone cannot be used as packaging material, as paper alone does not have any significant barrier properties effect . Therefore, in the field of flexible packaging, paper is mostly combined with other layers, such as plastic layers or metal layers, to meet the barrier properties. However, such wrapping paper laminates, such as the frequently used paper/aluminum/polyethylene constructions, are often difficult or even impossible to recycle due to the materials used.

More recently, more and more paper-based packaging has come on the market, which is equipped with only thin barrier and sealing layers, whereby the acceptable foreign matter/contaminant content in paper recycling according to EN643.1 The content specified here does not exceed the total packaging Maximum 5% by weight, see eg CPI's 'Recycling Design Tips', Confederation of Paper Industries, www.wrap.org.uk/packaging. It should also be noted that some coating materials (such as silicones and waxes, etc.) and some printing inks are also considered critical to the recycling process at less than 5%.

WO 2013/086950 A1 discloses a recyclable laminate with a "water-dispersible ionomer" (WPI) as adhesive, by which a thermoplastic is bonded to a substrate made of paper or aluminium . The laminate is recyclable as the paper layer and thermoplastic can be separated by WPI, but the recycling step requires high water preferably at 80°C and an action time of preferably 1 hour.

EP 3194164 B1 describes a laminate structure for food products with paper as material layer, aluminium as gas barrier layer and polymer layer as laminate. It particularly improves environmental compatibility by omitting ozone treatment in the case of polymer surface modification.

It is an object of the present invention to provide a recyclable wrapping paper laminate made of paper with high barrier properties to water vapour, oxygen and/or aroma, which can be easily produced and easily recycled.

This object is achieved by the barrier film comprising at least one substrate layer, a tie layer and a barrier layer, wherein the tie layer is arranged between the substrate layer and the barrier layer, wherein the substrate layer is mainly composed of polyethylene or polypropylene and The polyethylene or polypropylene content is at least 60% by weight, preferably at least 70% by weight, very particularly preferably at least 80% by weight of the substrate layer 4, of which at least one substrate layer is at least stretched, The proportion of the paper layer is 50% to 90% by weight of the packaging paper laminate, preferably 70% to 90% by weight, and the barrier film is combined with the paper layer with a hydrophilic adhesive layer, wherein the paper layer The side to the barrier film is uncoated. This is achieved with a polyolefin (PE or PP) content of 10 to 50% (preferably 10 to 30%) (ie significantly higher than previously considered necessary), and a predominant paper content in the packaging paper laminate ( High) blocking and recycling functions. In this way, it is possible to produce recyclable wrappers that still have a high barrier effect against water vapour, oxygen and/or aroma.

The barrier film can be designed asymmetrically with a substrate layer which is connected to the barrier layer via a connecting layer. Asymmetric barrier films can be made thinner, which means that the polymer content of the wrapping paper laminate can be reduced. In this case, the barrier layer is preferably arranged facing the paper layer and connected to the paper layer via an adhesive layer.

Alternatively, the barrier film is designed to have a symmetrical barrier layer, which is connected on both sides to a substrate layer via a connecting layer, wherein one of the substrate layers is connected to the paper layer via an adhesive layer . Symmetrical barrier films are easier to process because symmetrical films have less curl. The barrier layer is also well protected in the symmetrical structure.

The barrier layer can be implemented as a barrier coating in metallized form or in the form of a coating with silicon oxide or aluminum oxide, or as a layer made of a barrier polymer, preferably a polyamide or an ethylene-vinyl alcohol copolymer. In addition, the layer made of the barrier polymer can also be provided with a barrier coating in metallized form or in the form of a coating with silicon oxide or aluminum oxide, in order to further increase the barrier effect. This allows the barrier effect to be well matched to the corresponding barrier requirements of the wrapping paper laminate.

The barrier film is preferably stretched. This can be accomplished, for example, by co-extruding the barrier film as a whole and then stretching it. In addition, its barrier effect can also be increased by stretching the barrier polymer.

Many packaging applications require a sealing layer that can be bonded to the barrier film on the side remote from the paper layer. In order to improve the recyclability of the wrapping paper laminate, it is advantageous if the substrate layer consists mainly of PE, the sealing layer consists of PE, or if the substrate layer consists mainly of PP, the sealing layer consists of PP. This allows the production of wrapping paper laminates with particularly pure polymer content, which is beneficial for recyclability.

Advantageously, the sealing layer is also stretched. As a result, the thickness of the sealing layer can be reduced on the one hand, and on the other hand, the sealing layer can also be coextruded and stretched with the barrier film through this sealing layer, thereby simplifying production.

The present invention is explained in more detail below with reference to FIGS. 1 to 3 , which show, by way of example, not limitation, advantageous configurations of the invention. in this regard

Figure 1 shows a first embodiment of a wrapping paper laminate according to the invention,

Figure 2 shows the implementation of an asymmetric barrier film, and

Figure 3 shows the implementation of a symmetrical barrier film.

Figure 1 shows a wrapping paper laminate 1 according to the invention having a paper layer 2 and a barrier film 3 attached thereto, which achieves the desired barrier effect against water vapour, oxygen and/or aroma. A sealing layer 7 may be provided on the side of the wrapping paper laminate 1 facing away from the paper layer 2 . The paper layer 2 is bonded to the barrier film 3 with an adhesive layer 9 made of a hydrophilic laminating adhesive. A typical thickness of the wrapping paper laminate 1 is 50 μm to 150 μm.

The individual layers of the wrapping paper laminate 1 are explained in more detail below.

The paper layer 2 consists of paper with a basis weight of 30 to 360 g/m ² , preferably 30 to 100 g/m ² in the case of flexible packaging. Paper is known to be made of fibrous materials such as cellulose, pulp or waste paper. For the purposes of this application, cellophane is also understood to mean paper.

The paper layer is uncoated on at least one side (the side facing the barrier film 3 in the wrapping paper laminate 1). Uncoated means that the paper is substantially untreated on this side, in particular no plastic material has been applied to the paper, which would penetrate the paper, penetrate the paper fibers and bond to the paper fibers. This plastic coating is adhesively applied on this side, inseparable from the paper layer. Specifically, the face was neither coated with a barrier paint, sealant or other paint nor extrusion coated with a plastic layer. However, layers applied by layered silicates or minerals (clay coatings) often used in the paper industry are certainly present, as these generally do not interfere with paper recycling.

The laminating adhesive used for the adhesive layer 9 in the wrapping paper laminate 1 is hydrophilic. Hydrophilic laminating adhesives interact strongly with water and are usually (but not necessarily) water soluble as well. The hydrophilic laminating adhesive used in the wrapping paper laminate 1 according to the present invention loses its adhesion through water, either due to chemical mechanisms, such as breaking of hydrogen bonds, or because the laminating adhesive is Dissolves in water.

The hydrophilic laminating adhesive can be modified based on starch, sugar derivatives, cellulose, amino resins, (poly)acrylates, polyvinyl alcohol (PVOH), polyvinyl acetate, polyacrylic acid, maleic acid Ethylene copolymer, methyl cellulose, carboxymethyl cellulose, carboxyl functional polyester, polyethylene succinate, polybutylene succinate, ionomer or hydrophilic polyurethane preparation.

Hydrophilic laminating adhesives for extrusion lamination can also be used, such as, but not limited to, ethylene copolymers with comonomers containing polar groups, such as ethylene vinyl acetate (EVA), ethylene - Butyl acrylate (EBA), ethylene-acrylic acid copolymer (EAA), or polyethylene/polypropylene grafted with maleic anhydride (PE-G-Mah, PP-G-Mah).

The laminating adhesive is of course chosen to provide sufficient adhesion between the paper layer 2 and the barrier film 3 to prevent undesired delamination of the wrapping paper laminate 1 in use. The adhesive layer 9 should preferably achieve an adhesive adhesion between the paper layer 2 and the barrier film 3 of at least 1 N/15mm, preferably at least 1.5 N/15mm.

Adhesive adhesion was determined by peel test. In the peel test, a test strip of wrapping paper laminate 1 was pulled apart at the free ends of paper layer 2 and barrier film 3 . The free end is clamped in a pulling machine and pulled apart at a specific angle (eg 90°) and the force is measured. The test strips were 15mm wide and the adhesive adhesion was x N/15mm. The specification for adhesive adhesion here is the nearly constant peel value, not the maximum tear value that occurs as a force peak at the start of the peel test. Typically, in order to determine adhesive adhesion, multiple peel tests are also performed, and the verified adhesive adhesion is determined as the average of the individual measurements. For example, a peel test is performed according to the ASTM F904 standard.

Since paper is used in the wrapping paper laminate 1, a liquid laminating adhesive can be used to create the adhesive layer 9 between the paper layer 2 and the barrier film 3, especially one dissolved in water or a suitable solvent Lamination adhesive. After applying the liquid laminating adhesive and bonding the paper layer 2 and barrier layer 3 together, the laminating adhesive is dried, wherein the water or solvent can diffuse through the paper. After drying, the adhesive layer 9 remains to establish the connection between the paper layer 2 and the barrier film 3 . However, non-liquid laminating adhesives can also be used to produce the adhesive layer 9 as long as they are hydrophilic.

Extrusion lamination may also be considered, in which molten laminating adhesive is extruded as a molten liquid onto paper layer 2 or barrier film 3, or both, at elevated temperatures above 180°C, and the paper layer is then extruded. 2 and barrier film 3 together. After the lamination adhesive is cured, the adhesive layer 9 is formed.

The barrier film 3 consists of at least one stretched substrate layer 4 mainly made of polyethylene (PE) or mainly polypropylene (PP), a tie layer 5 and a barrier layer 6 ( FIG. 2 ). The thickness of the barrier film 3 is generally 10-40 μm.

The barrier film 3 can be designed asymmetrically (as shown in FIG. 2 ), with a substrate layer 4 , a barrier layer 6 and a connection layer 5 disposed therebetween, wherein the connection layer 5 is directly connected to the substrate layer 4 and the barrier layer 6 . In the case of an asymmetric barrier film 3, the barrier layer 6 in the wrapping paper laminate 1 is preferably arranged to face the paper layer 2 and is directly connected to the uncoated side of the paper layer 2 by the adhesive layer 9, but also may face the sealing layer 7 . However, the barrier film 3 can also be designed to be symmetrical (as shown in FIG. 3 ). In this case, the barrier layer 6 is connected to the base material layer 4 (which may also be different) on both sides via the connecting layer 5 respectively. In a symmetrical implementation, the uncoated side of the paper layer 2 is directly connected to the substrate layer 4 of the barrier film 3 via the adhesive layer 9 .

In one possible configuration, the barrier layer 6 is a barrier coating applied to the connection layer 5 in the form of a metallization (eg with aluminium) or a coating of silicon oxide (SiOx) or aluminium oxide (AlOx). This configuration is preferably used with an asymmetric barrier film 3 . By means of the barrier coating, a barrier layer 6 that is only a few nanometers thin (typically about 10 to 50 nm) is formed on the connecting layer 5 . Metallization can be accomplished, for example, by the known vacuum metallization. For example, a SiOx or AlOx coating can be applied using a chemical vapor deposition process or by evaporation in a vacuum. Of course, other methods of making barrier coatings are also possible. The barrier coating can also be additionally coated with a protective varnish to prevent microcracking, which can impair the barrier function. Oxygen transmission rates (oxygen transmission rate, OTR) of less than 2 cm ³ /m ² /d (at 23° C. and 75% relative humidity on both sides) and (at 38° C., both sides) can be achieved using this barrier coating. A low water vapor transmission rate (WVTR) of less than 3 cm ³ /m ² /d at 90% relative humidity, where d represents a day, ie 24 hours.

In another possible configuration, the barrier layer 6 is a layer made of a barrier polymer (used in both asymmetric and symmetric barrier films 3 ), ie a polymer with sufficient barrier properties, in particular oxygen barrier and/or aroma. The barrier polymer is preferably polyamide (PA) or ethylene vinyl alcohol copolymer (EVOH). EVOH is preferably used as the barrier polymer. The thickness of the barrier polymer is up to 20% of the total thickness of the barrier film 3, preferably 5 to 10%, ie for example in the case of a barrier film thickness of 10-40 μm the thickness of the barrier polymer is up to 2 to 8 μm. Using a barrier polymer as barrier layer 6, not only low water vapor permeability (similar to or better than above) can be achieved, but also (at 23°C, 75% relative humidity on both sides) less than 2 cm ³ /m ² /d Low oxygen permeability (oxygen transmission rate, OTR) and high aroma barrier properties. There is no objective measure of aroma barrier, but rather the effect as aroma barrier is determined subjectively by odor tests.

If a barrier layer 6 made of a barrier polymer is provided in the barrier film 3, the barrier layer 6 in the asymmetric or symmetric barrier film 3 may additionally be coated with a barrier coating, in particular metallized (eg aluminium), or aluminum oxide or silicon oxide coating. The barrier effect of the barrier film 3 can thus be further improved, in particular the OTR and WVTR can thus be further significantly reduced, ie less than 1 cm ³ /m ² /d, respectively. In this implementation, the barrier coating can also be additionally coated with a protective lacquer.

The substrate layer 4 is mainly made of polyethylene (PE) or polypropylene (PP) with a polyethylene content or polypropylene content, respectively, of at least 60% by weight, preferably at least 70% by weight of the substrate layer 4 , and very particularly preferably At least 80% by weight. The higher the polyethylene or polypropylene content (ie the purer the substrate layer 4), the better the recyclability. The thickness of the base material layer 4 is preferably 5 to 35 μm, wherein also base material layers 4 of different thicknesses and/or different structures can be used in the symmetrical barrier film 3 . However, in a symmetrical structure, the two substrate layers 4 are preferably made of the same main component PE or PP. Conventional additives (eg, slip additives, anti-blocking additives, fillers, etc.) may be added to the substrate layer 4 . Different polyethylene types or polypropylene types can also be used for the substrate layer 4, in each case as mixtures or coextrusions. Likewise, in addition to the respective main constituents PE or PP, the substrate layer 4 may also comprise respective compatible polyolefin materials.

Considered as the type of polyethylene in the substrate layer 4 are, for example, HDPE (high density polyethylene with a density of 0.94-0.97 g/cm ³ ), MDPE (medium density polyethylene), LDPE (density of 0.915-0.935 g) / ^cm3 ), LLDPE (linear low density polyethylene with densities between 0.87–0.94 g/ ^cm3 ) or mLLDPE (linear metallocene low density polyethylene). Preferably HDPE or MDPE is used. Suitable polypropylene types in the substrate layer 4 come into consideration, for example, atactic, syndiotactic or isotactic PP.

As a PE-compatible polyolefin material any type of polyethylene is considered in principle, especially ethylene copolymers, such as ethylene vinyl acetate (EVA), ethyl methacrylate (EMA), ethylene/acrylic acid copolymers (EAA) or ethylene-butyl acrylate copolymer (EBA). Polypropylene (PP) or cyclic olefin copolymers (COC) can likewise be used in an amount of up to 20% by weight as PE-compatible polyolefin material. In the case of PP, it is preferred to use polypropylene random copolymers with ethylene as comonomer (usually 5 to 15%), polypropylene copolymers with ethylene or with linear PE types such as mLLDPE, LLDPE or HDPE Polypropylene homopolymer with sufficient compatibility to achieve at least limited recyclability.

PP copolymers, such as random copolymers and block copolymers, come into consideration as PP-compatible polyolefin materials. Adding up to 20% polyethylene also has little effect on recyclability.

If the base material layer 4 contains a polyolefin material compatible with PE or PP, the content of the main component polyethylene (PE) or polypropylene (PP) in the base material layer 4 is preferably at least 60% by weight (based on the base material layer) 4), preferably at least 70% by weight, most preferably at least 80% by weight, to improve recyclability. PE or PP and the respective compatible polyolefin material may be present in the substrate layer 4 as a mixture.

However, the substrate layer 4 may also be of a multi-layer (extruded or co-extruded) construction, with one (or more) PE or PP layer and one (or more) layers of a compatible polyolefin material layer made.

A cavitation agent can also be added to the main component PE or PP of the base material layer 4, wherein the cavitation agent is added to the base material layer 4 in an amount of 5-30 wt %, preferably 15-25 wt %. Polymers that are incompatible with PE or PP (ie polymers that maintain a barrier in the PE or PP matrix), such as polyamides (PA), polyesters (eg PET or PBT), polylactic acid (PLA), come into consideration as cavitation agents ). Mineral cavitation agents such as calcium carbonate or mica can also preferably be used. The cavitating agent is usually in the form of a fine powder, embedded in a PE or PP matrix as a masterbatch before extrusion, and mixed with PE or PP particles.

If a cavitated PE or PP layer is used in the substrate layer 4, it is preferably surrounded on one or both sides by a non-cavitated PE or PP layer. One conceivable configuration of the substrate layer 4 of the laminate layer 3 is, for example, a cavitated PE layer, which is joined on one side to a non-cavitated PE layer (eg coextrusion), wherein the material is laminated in a wrapper 1 The hollowed PE layer faces the paper layer 2. Another preferred configuration of the substrate layer 4 is, for example, a cavitated PE layer, which is joined (eg coextruded) on both sides with a non-cavitated PE layer. Similarly, there is a structure in which PP is the main component in the base material layer 4 . The use of a cavitation layer in the substrate layer 4 can also improve the sealing properties of the wrapping paper laminate 1 .

The sum of PE or PP, cavitation agent, any additives and possibly compatible polyolefin material in the substrate layer 4 is of course only 100% by weight together. The decisive factor here is the content of the main component polyethylene or polypropylene, on which the other ratios must be based.

At least the substrate layer 4 in the barrier film 3 is uniaxially or biaxially stretched, ie in the machine direction (MDO) (usually the machine direction or extrusion direction) and/or in the transverse direction (TDO) (rotated by 90° with respect to the machine direction) stretch. If a barrier polymer is used as the barrier layer 6 in the barrier film 3, the entire barrier film 3 is preferably stretched. In the case where the tie layer 5 or the barrier layer 6 is coated, it is stretched before coating. The degree of stretch in the machine direction and the cross direction need not be the same. The stretch in the machine direction is preferably at least 4:1 to 8:1. The stretch in the transverse direction is preferably at least 5:1 to 10:1. Uniaxial MDO stretching is preferred because uniaxial stretching is easier than biaxial stretching.

By stretching the barrier film 3 or at least the substrate layer 4 of the barrier film 3, the weight proportion of the polyolefin (PE or PP) in the wrapping paper laminate 1 can be kept low, since only by stretching it is possible to produce thin But hard film.

It is known that the barrier effect can also be significantly improved by stretching the barrier polymer. By stretching the barrier polymer, the barrier value is increased by about three to four times compared to the same type of unstretched barrier polymer, thereby allowing the use of a cheaper barrier polymer with the same barrier effect. As a result, the cost of the wrapping paper laminate 1 can also be significantly reduced.

The connection layer 5 is used to connect the barrier layer 6 and the base material layer 4 . Sufficient adhesive adhesion should be achieved here, in particular in order to ensure that undesired delamination of the barrier film 3 is prevented. Suitable polar tie layers 5 preferably consist of polymers of increasing polarity, for example based on polyolefins grafted with maleic anhydride (eg PE or PP), ethylene vinyl acetate (EVA), ethylene/acrylic acid Copolymer (EAA), ethylene-butyl acrylate (EBA), or similar polyolefin copolymer. The material of the connection layer 5 is preferably selected according to the main components of the base material layer 4 . The thickness of the connection layer 5 is at most 10% of the total thickness of the barrier film 3 , for example 1 to 5 μm in the case of a thickness of the barrier film 3 of 10 to 40 μm.

When the main component of the base material layer 4 is PE, the sealing layer 7 is preferably polyethylene, such as LLDPE, LDPE, MDPE or HDPE. Also conceivable are mixtures of different PE types in the sealing layer 7, such as multilayer sealing layers 7 made of the same or different PE types. If the main component of the substrate layer 4 is polypropylene, the sealing layer 7 is preferably polypropylene, eg unstretched PP (CPP). In this case, the sealing layer 7 can also be a mixture of different PPs and/or be of multi-layer construction. The thickness of the sealing layer 7 should be as small as possible in the sense of better recyclability, in particular less than 50 μm, preferably less than 30 μm.

If desired, a connecting layer 8 (as shown in FIG. 3 ), for example, can also be provided between the barrier film 3 and the sealing layer 7 , as described above, to improve adhesion.

In order to make the wrapping paper laminate 1 easy to recycle, the polymer content of the wrapping paper laminate 1 (mainly the barrier film 3 and, if present, the sealing layer 7) should be between 10% by weight of the wrapping paper laminate 1 and 50% by weight, preferably at most 30% by weight, particularly preferably at most 20% by weight. Therefore, the wrapping paper laminate 1 according to the present invention follows a different protocol than that recommended in the prior art, wherein the polymer content needs to be kept below 5% by weight. However, in order to achieve good recyclability, the paper layer 2 is uncoated on the side facing the barrier film 3 and is connected to the barrier film 3 by a hydrophilic adhesive layer 9 .

When recycling the packaging paper laminate 1, it is usually macerated in water at a specific water temperature and a specific time period after mechanical comminution (pulp process). Due to the properties of the packaging paper laminate 1 according to the invention, the paper layer 2 can be separated from the barrier film 3 (together with all layers and potential contaminants for paper recycling) during the pulping process of recovery. The hydrophilic adhesive layer 9 reacts with water during pulping, loses its adhesion or completely dissolves in water, thereby separating the paper layer 2 from the barrier film 3 . The paper layer 2 can thus be dissolved in water and form pulp, from which in turn recycled paper can be produced. It is advantageous for the recycling of the packaging paper laminate 1 if the adhesive layer 9 loses its adhesion or dissolves sufficiently at a water temperature of 40° C. for at most 20 minutes, preferably at most 10 minutes, particularly preferably at most 5 minutes, so that The paper layer 2 and the barrier film 3 are easily separated from the sealing layer 7 .

After separation in the pulping process in paper recycling, the recovered paper will not be grayed due to the metallized layer (if any) remaining on the separator 3, which will inevitably occur on the surface of the paper in the barrier metallization layer.

The barrier film 3 separated from the paper layer 2 in the paper recycling, optionally with a sealing layer 7, can be sent to a further recycling process in order to be able to recover the polyolefin (main component PE or PP) contained therein. By way of example in the best possible classification of the barrier film 3 and the sealing layer 7, the main components of which are PE or PP and materials compatible therewith, the barrier film 3, optionally with The sealing layer 7 can also be recovered easily and inexpensively using a conventional method of mechanical recovery. The ease of recovery of the polyolefin stream exiting the paper recovered pulp is not affected by the small thickness of the barrier layer 6 (if provided) in the barrier film 3 .

The barrier film 3 is advantageously produced by co-extrusion, since this enables a particularly simple and cost-effective production. Preferably known blown film or flat film extrusion processes are used. In this case, the individual layers of the symmetrical or asymmetrical layer structure of the barrier film 3 as described above (ie the substrate layer 4 and the tie layer 5 and optionally also the barrier layer 6 made of a barrier polymer ) up to a possible coating, preferably co-extrusion in one step. After co-extrusion, this laminate is uniaxially or biaxially stretched. After stretching, a barrier coating can also be applied, either as the barrier layer 6 on the tie layer 5 or on the barrier polymer of the barrier layer 6 .

The barrier film 3 can also be co-extruded with the sealing layer 7 in one step. In this case, the sealing layer 7 with the barrier film 3 is also stretched. Alternatively, the sealant layer 7 may be bonded to the membrane via extrusion lamination (extrusion of the sealant layer 7 onto the barrier film 3) or during lamination (the barrier film 3 is attached to the sealant layer 7 with a laminating adhesive) The stretched barrier film 3 is attached. When laminating the sealing layer 7, a stretched sealing layer 7 may also be used.

Particularly preferably, the sealing layer 7 is integrated directly into the barrier film 3 during manufacture, for example by coextrusion, on the side of the barrier film 3 opposite the barrier layer 6 . The sealing layer 7 can thus be made thinner and the total polymer content in the wrapping paper laminate 1 can be lower than in the case of subsequent application of the sealing layer 7, which in addition simplifies production.

The stretching of the barrier film 3 (possibly with the sealing layer 7 ) can be carried out in-line (ie directly after co-extrusion) or off-line (ie at a later point in time after co-extrusion). In the case of biaxial stretching here, it may be stretched in the machine direction first and then in the transverse direction, or may be stretched in both directions at the same time. Stretching typically occurs at about 10°C to 30°C, usually about 20°C, below the lowest melting point of the plastic in barrier film 3 or optional sealing layer 7 (about 128°C to 130°C in the case of HDPE). In any case, the stretching takes place before the possible coating of the barrier layer 6 and/or the tie layer 5 .

In the case of cavitated PE or PP, the uniaxial or biaxial stretching in the substrate layer 4 produces microcavities in the PE or PP in a known manner due to the cavitating agent. It was found here that the density of the substrate layer 4 can be significantly reduced by microcavities to values between 0.4-0.85 g/cm ³ . The barrier film 3 can thus be made lighter, which further reduces the polymer content.

The paper layer 2 is laminated with a barrier film 3 (optionally with a sealing layer 7). For this purpose, the hydrophilic laminating adhesive can be applied in liquid form to the paper layer 2 or the barrier film 3, or to both, for example by roller or pressure application or by spraying. Thereafter, the paper layer 2 and the barrier film 3 are pressed against each other, for example between two rollers, to produce the wrapping paper laminate 1 . If desired, the laminating adhesive can then be dried to form the adhesive layer 9, for example by passing it through a thermal tunnel.

Alternatively, paper layer 2 and stretch barrier film 3 can be bonded using an extrusion lamination process when a suitable laminating adhesive is used. In extrusion lamination, molten laminating adhesive is extruded onto paper layer 2 or barrier film 3 or both, and then paper layer 2 and barrier film 3 are pressed together, for example between two rolls , to produce wrapping paper laminates 1. The lamination adhesive can then be cooled down, usually assisted by cooled rollers.

The sealing layer 7 of the wrapping paper laminate 1 can also be laminated after the lamination of the paper layer 2 and the barrier film 3 .

In an exemplary embodiment, a barrier film 3 with a thickness of 10-40 μm is used, which has the main component PE (at least 60% by weight PE content), preferably HDPE, accounting for at least 60% of the thickness of the stretched barrier film 3 % of substrate layer 4. A polar PE or PP material (depending on the main composition of the substrate layer 4 ) is used as the connecting layer 5 . A barrier layer 6 made of EVOH (barrier polymer) is connected to the connecting layer 5 . The barrier film 3 is coextruded and then stretched uniaxially or biaxially. In addition, the barrier polymer can be coated with a barrier coating (metallization, SiOx or AlOx) after stretching. In an alternative configuration, a barrier coating is applied to the stretched substrate layer 4 with the tie layer 5 . The at least partially stretched barrier film 3 is attached to the paper layer 2 with an adhesive layer 9 made of a hydrophilic laminating adhesive. In addition, a sealing layer 7 made of PE material can be provided on the side of the paper packaging laminate 1 facing away from the paper layer.

Claims (11)

1. A recyclable packaging paper laminate consisting of a paper layer ( ² ) and paper having a basis weight of 30-360 g/m and a barrier film (3) attached thereto, characterized in that the barrier film (3) At least one substrate layer (4), a connection layer (5) and a barrier layer (6) are provided, wherein the connection layer (5) is arranged between the substrate layer (4) and the barrier layer (6) , the substrate layer (4) is mainly composed of polyethylene or polypropylene, wherein the content of polyethylene or polypropylene is at least 60% by weight of the substrate layer (4), preferably at least 70% by weight, very particularly preferably At least 80% by weight, at least one substrate layer (4) of the barrier film (3) is at least stretched, and the proportion of the paper layer (2) is 50% by weight of the wrapping paper laminate (1) % to 90% by weight, preferably 70% to 90% by weight, and the barrier film (3) is connected to the paper layer (2) with a hydrophilic adhesive layer (9), wherein the paper layer (2) The side facing the barrier film (3) is uncoated. 2. The recyclable wrapping paper laminate according to claim 1, wherein the barrier film (3) is designed to have a substrate layer (4) asymmetrically, the substrate layer (4) The connection layer (5) is connected to the barrier layer (6). 3. The recyclable wrapping paper laminate according to claim 2, characterized in that the barrier layer (6) is arranged facing the paper layer (2) and communicated with the adhesive layer (9) through the adhesive layer (9). The paper layer (2) is connected. 4. The recyclable wrapping paper laminate according to claim 1, characterized in that the barrier film (3) has a barrier layer (6) symmetrically, the barrier layer (6) passing through on both sides respectively The tie layer (5) is connected to the substrate layer (4), and one of the substrate layers (4) is connected to the paper layer (2) via an adhesive layer (9). 5. The recyclable wrapping paper laminate according to any one of claims 1 to 4, characterized in that the barrier layer (6) is designed as a barrier coating which is metallized form or in the form of a coating with silica or alumina. 6. The recyclable wrapping paper laminate according to any one of claims 1 to 4, characterized in that the barrier layer (6) is designed as a layer made of a barrier polymer, the barrier polymer The compound is preferably a polyamide or an ethylene-vinyl alcohol copolymer. 7. The returnable wrapping paper laminate according to claim 6, wherein the barrier polymer layer is provided with a barrier coating in the form of a metallization or a coating with silica or alumina. 8. The returnable wrapping paper laminate according to claim 6, wherein the barrier film (3) is stretched. 9. The recyclable packaging paper laminate according to any one of claims 1 to 8, characterized in that the barrier film (3) is connected to the sealing layer (7) on the side facing away from the paper layer (2) connect. 10. The recyclable wrapping paper laminate according to claim 9, characterized in that when the substrate layer (4) is mainly composed of polyethylene, the sealing layer (7) is composed of polyethylene, or When the base material layer (4) is mainly composed of polypropylene, the sealing layer (7) is composed of polypropylene. 11. The returnable wrapping paper laminate according to claim 9 or 10, wherein the sealing layer (7) is stretched.

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